1. Field of the Invention
The present invention relates to a semiconductor power device and a manufacturing method thereof, and more particularly, to a semiconductor power device and a manufacturing method thereof to reduce the number of masks in the manufacturing process.
2. Description of the Prior Art
A trench metal-oxide-semiconductor field effect transistor (Trench MOSFET) is a common semiconductor power device. In the trench metal-oxide-semiconductor field effect transistor, a gate electrode is disposed in a trench of a substrate, and a source electrode and a drain electrode are respectively disposed at an upper side and a lower side of the gate electrode. A channel is vertically formed between the source electrode and the drain electrode. Accordingly, some advantages are provided by this structure, such as a high voltage-withstand ability, a low on-resistance, and a larger current. As a result, the trench metal-oxide-semiconductor field effect transistors are widely applied in power management, such as switching power supplies, integrated circuits used in power management, backlight power supplies, and motor controllers.
In the prior art, the number of masks utilized in the manufacturing processes of the trench metal-oxide-semiconductor field effect transistors is generally up to eight or nine. For example, the masks includes a trench mask, a body mask, a source mask, a poly 1 mask, a poly 2 mask, an oxide mask, a contact mask, a metal mask, and so on. In addition, in order to reduce the capacitance between the gate electrode and the drain electrode and to improve the breakdown voltage of the transistor, additional manufacturing processes with other masks are performed to form a shield electrode under the gate electrode. On the other hand, in order to avoid the channeling effect between the trench metal-oxide-semiconductor field effect transistors and other components, some manufacturing processes with other masks are required to define a termination structure for isolating different components.
Each of the manufacturing processes with the masks requires a plurality of steps, such cleaning steps, photoresist coating steps, exposure steps, developing steps, etching steps, photoresist stripping steps, or checking steps. Thus, the complexity and the processing time of the manufacturing process are increased due to the larger number of the masks, and this undesirably results in a higher manufacturing cost and a low yield. Therefore, a new manufacturing process is required to simplify the conventional processes and to reduce the number of the masks.